In recent years, research on electrochemical cells has actively been conducted. For example, polymer electrolyte membrane-electrolyze cells (PEMECs) of electrochemical cells are superior in responsiveness to renewable energy of photovoltaic power generation and the like and so are expected to be utilized for generating hydrogen of large-scale energy storage systems. To ensure sufficient durability and water electrolysis performance, platinum nano-particle catalyst is commonly used for a cathode of PEMEC and a particulate iridium based catalyst is commonly used for an anode thereof.
One big challenge for widespread use of PEMEC is the cost reduction by reducing the amount of use of noble metal catalysts.
Powder of iridium black or iridium black oxide is used for a conventional PEMEC anode electrode and the powder is made a slurry by a solvent and applied onto a base material and then the solvent is removed by a calcination process or the like to be carried and supported on the base material. This is not sufficient for close contact between a catalyst layer and the base material and particularly in a high-load environment like operating for a long time in a high current density, catalytic activity is degraded with gradual desorption of catalyst particles, posing a grave problem of durability. To ensure sufficient water electrolysis efficiency and durability, a large quantity of catalyst is needed. Further, the particle size is mostly a dozen or so nm or more and sufficient holes are not obtained and thus, the material transport indispensable for an electrode reaction is inhibited, posing a problem that sufficient water electrolysis efficiency is not obtained.